1. Field of the Invention
The present invention relates to a radiation-sensitive resin composition and, more particularly, to a radiation-sensitive resin composition suitable as a chemically-amplified resist useful for microfabrication utilizing various types of radiation, for example, deep ultraviolet rays such as a KrF excimer laser, ArF excimer laser, or F2 excimer laser, X-rays such as synchrotron radiation, or charged particle rays such as electron beams.
2. Description of Background Art
In the field of microfabrication represented by the manufacture of integrated circuit devices, lithographic technology enabling microfabrication with a line width of 0.20 μm or less has been demanded in order to increase the degree of integration in recent years.
In a conventional lithographic process, near ultraviolet rays such as i-line radiation have been generally used. However, it is difficult to perform microfabrication with a line width of sub-quarter micron using near ultraviolet rays.
Therefore, in order to enable microfabrication with a line width of 0.20 μm or less, utilization of radiation with a shorter wavelength has been studied. As examples of radiation with a shorter wavelength, deep ultraviolet rays represented by a line spectrum of a mercury lamp and an excimer laser, X-rays, electron beams, and the like can be given. Of these, a KrF excimer laser (wavelength: 248 nm), an ArF excimer laser (wavelength: 193 nm), and an F2 excimer laser (wavelength: 157 nm) have attracted attention.
As a radiation-sensitive resin composition applicable to such an excimer laser radiation, a number of resists utilizing a chemical amplification effect between a component having an acid-dissociable functional group and a photoacid generator which generates an acid upon irradiation have been proposed. Such a resist is hereinafter called a chemically-amplified resist.
In such a chemically-amplified resist, a photoacid generator is known to greatly affect the functions of the resist. In these days, onium salt compounds which generate an acid upon irradiation at a high quantum yield and exhibit relatively high sensitivity are widely used as photoacid generators for chemically-amplified resists.
An onium salt compound used as a photoacid generator contains an onium cation and a counter anion. The structure of such an onium salt compound has been extensively studied. In particular, the onium cation is known not only to control the quantum efficiency of acid generation during irradiation, but also to affect the properties of the onium salt compound such as, for example, solubility in a solvent for resists, melting point, thermal decomposition temperature, chemical stability to various resist additives such as an acid diffusion controller, and affinity with a resin component for a resist. The onium cation thus greatly affects the functions of chemically amplified resists.
Onium salts of which the onium cation is a 4-hydroxyphenylsulfonium cation, 4-hydroxynaphthylsulfonium cation, or a derivative thereof absorb only a small amount of rays in the deep ultraviolet region typified by an ArF excimer laser. This enables the resist containing such an onium salt to exhibit high resolution and produce excellent rectangular resist patterns, but lowers the sensitivity of the resist. On the other hand, onium salts of which the onium cation is a triphenylsulfonium cation or its derivative can afford high sensitivity to the resist, but absorb a larger amount of rays in the deep ultraviolet region typified by an ArF excimer laser, disenabling the resist to exhibit high resolution.
In view of recent progress in microfabrication of semiconductor devices, development of a radiation-sensitive resin composition useful as a chemically amplified resist which is applicable to deep ultraviolet rays typified by an ArF excimer laser and exhibits excellent basic properties as a resist is an important subject.
An object of the present invention is to provide a novel radiation-sensitive resin composition useful as a chemically amplified resist exhibiting excellent sensitivity and resolution to deep ultraviolet rays typified by an ArF excimer laser, and superior basic properties as a resist such as producing a pattern shape.